Paper-pulp digester



UNITED STATES PATENT OFFICE.

FREDERICK S. LYMAN, OF AUGUSTA, MAINE.

PAPER-PU LP DIG EASTER.

SPECIFICATION forming part of Letters Patent No. 620,243, dated February 28, 1899. Application filed June 23, 1893- Serial No.4'78,676. (No model.)

To all whom it may concern..-

Be it known that I, FREDERICK S. LYMAN, of Augusta, in the county of Kennebec and State of Maine, have invented certain new and useful Improvements in Paper-Pulp Digesters, of which the following is a full, clear, and exact description, whereby any one skilled in the art can make and use thesarne.

My invention relates to digesters for treating paper-pulp, wood, or other fiber-yielding material in a metallic boiler under heat and pressure and with an acid, such as sulfite of lime. Such digesters have usually been made with a steel shell and have been lined with various materials,as sheet-leadpcment'bricks, and tile, for the purpose of shielding the metallic shell from the attacks of the acid, which otherwise corrodes the iron or steel of the boiler and in time destroys it.

My invention consists in an improved digester-lining that shall be non-expansible, a non-conductor of heat, and acid-proof; and it further consists in the combination of a shell with such a lining and in details of the several parts making up the whole and in the combination of such parts, as more particularly hereinafter described, and pointed out in the claim.

Referring to the drawings, Figure 1 is a de tail view in cross-section of a digester, showing the improved lining. Fig. 2 is a detail view of an improved manner of sealing the joints in the lining.

In the accompanying drawings the letter a denotes a digester-shell,made usually of steel or like material and of the ordinary form and provided with the usual necessary inlets and outlets and attachments necessary to the use of the apparatus for the purpose of treating paper-pulp with an acid solution under heat and pressure. Within this shell is fixed a lining b of pulp made of fibrous material substantially such as has been used in making paper, paper barrels, and like articles of pulp. A vegetable fiber is preferred for the reason that a lining made up of such material can be made continuous, is a non-conductor of heat, non-expansible, can be readily rendered acid-proof, and will not shrink or crack when exposed to extreme changes of temperature.

A serious objection to lead as a lining for such digesters has been the fact that it expands under the heat to which it is subjected, does not again contract, and by wrinkling cracks and is soon of no value as a protector to the iron shell. A serious difficulty has been encountered in the use of cement or brick for the reason that the cement wears away under the wash of the fluid contents and the action of the heat, and the joints in the tile or brick used to protect the cement require a supplemental protection for the cement that holds the brick together, and this in turn, if of lead, as is usually the case, soon wears away under the conditions of use and leaves the shell again practically unprotected.

My improved lining of paper-pulp may be applied in a continuous sheet and compacted to any desired degree, mixed with an acidproof material, and hardened to such an extent as to resist the action of heat and steam as well as the Wash of the materials in the digester. Within this lining b may be used a supplemental lining c of bricks or tile laid up in cement in the usual manner, thejoints d between the bricks being protected next the inside by a filling or calking m, of lead or like acid-proof material, located between the lining b and supplemental lining c.

The lining b may be made in sections and in such case formed to shape under heat and pressure by means that enable a greater density to be given to the lining and its surface more successfully treated by means that render it hard and better suited to resist any erosive action of materials within the digester. A form of joint between the sections is shown in 'plan View in Fig. 2, the edges 6 f of two contiguous sections being arranged with irregular surfaces that fit together, a socket 9 being left, in which a strip h, of lead, is arranged. On the face of the lining farthest from the shell a strip '5 of acid-resistin g metal, as bronze, tin, lead, antimony, or the like, is placed, and underneath a cylindrical or angular piece or length j of lead is arranged opposite to the packing-strip h. Under the application of heat this stripj of lead expands and, pressing outward, closes the lapped parts of the lining b closely upon each other and upon the packing-strip h, and thus effectually closes the seam against the passage of any fluid. The meeting faces of these parts may be roughened or corrugated, if desired, to more effectually close the joint, the strip j as it expands causing the roughened parts to interengage.

Although it is preferred to make the lining b of vegetable fiber, it is not limited wholly to such material; but the lining may be to a greater or less degree composed of a mixture of other fibrous material that possesses like qualities that render it a non-conductor of heat, acid-proof, and nou-expansible under the application of heat.

, The lining b of the digester may be constructed of paper-pulp or like material in a single layer of the desired thickness, or several layers may be provided, each also being treated with an acid-proof material and secured to the shell of the digester and to each other with an acid-proof cement. In this form the several layers Will be so secured together that the joints of union between the parts shall be broken or the edges overlap each side, so as to provide a practically solid lining in that an effective barrier would be provided to the passage of any fluid from within the digester to the inside surface of the outside shell of the same.

Any of the Well-known acid-proof materials may be used for coating the lining of the shell, and where a plural number of layers are provided any well-known acid-resisting cement may be used for cementing the several layers together. I do not claim any original cement to be used for this purpose; but

it may consist of silicate of soda and cement composed largely of monosulfite of lime; but as very little acid would ever reach this lining it is not of vital importance that the ocment should be absolutely acid-proof, this lining being covered with brick suitably laid to prevent the passage of liquids contained Within the boiler. The principal object of the paper-pulp lining is to prevent the shell of the boiler from being heated by the contents, and consequently prevent its contraction and expansion. This Will prevent the brick lining from being cracked to any extent and efiectually obviate the difliculty of the destruction of this brick lining by the contraction and expansion of the shell.

I claim as my invention In combination with the shell of a digester or like apparatus, a sectional lining made of paper-stock compressed to shape with the edges of the lapped sections of the lining having interengaging parts, a packing-strip located in a socket between the meeting edges of the sections, a compressing-strip of lead or like expansible metal overlying the inner surface of the lapped parts of the sections directly opposite the packing-strip, and an inner covering-layer all substantially as described.

FREDERICK S. LYMAN.

\Vitnesses:

CHAS. L. BURDETT, ARTHUR B. JENKINS. 

